EFFECT OF ADJUVANT ENDOCRINE THERAPY ON ESTROGEN RECEPTOR-NEGATIVE, PROGESTERONE RECEPTOR-POSITIVE AND HER2 NEGATIVE BREAST CANCER PATIENTS

Objective: The purpose of this study was to analyze the efficacy of adjuvant endocrine therapy in ER-negative, PR positive and human epidermal growth factor receptor-2 (HER2) negative (ER-/PR+, HER2-) breast cancer patients retrospectively. Methods: In this single-center retrospective study, 1348 female HER2 negative breast cancer patients who were treated from August 1st, 1996 to April 30th, 2016 were included. Patients were characterized as "HER2 negative" if the semi-quantitative score of human epidermal growth factor receptor-2 (HER2) was absent or showed weak or incomplete membrane staining in breast cancer tissue. Tissue which was classified as ER or PR positive had 1% or more cells with nuclear staining as determined by immunohistochemical analysis. "HER2 negative" patients were divided into three subgroups based on the expression level of ER and PR: ER+/PR (+,-), ER-/PR+ and ER-/PR-. The clinical characteristics of each patient were investigated, cumulative survival rates of the three subgroups were analyzed by the Kaplan-Meier method, and the differences in cumulative survival was assessed using the Log-rank method. Results: The 5-year overall survival rates of all patients in the study were 88%; with 92%, 90% and 87% of those in ER+/PR (+,-), ER-/PR+ and ER -/PR-groups respectively living longer than 5 years. The 5-year overall survival rates among the three subgroups were significantly different (P=0.047) as determined by univariate analysis. However, no significant difference was found between ER-/ PR+ and ER -/PR-groups (P=0.35). Conclusion: Taken together, ER-/PR+ female breast cancer patients may have improved survival outcomes from adjuvant endocrine therapy.